Without limiting the scope of the invention, its background is described in connection with compound semiconductor Heterojunction Bipolar Transistors, as an example.
Heretofore in this field Heterojunction Bipolar Transistors (HBTs) have not been widely manufactured in production volumes. Problems with reproducibility and reliability of HBTs in the past have limited the use of the devices in production quantities despite the HBT's advantages of efficiency, power, and linearity over FET devices. Reproducibility in the fabrication of semiconductor devices demands the ability to repeat processes from wafer to wafer and lot to lot. In the case of an epitaxial GaAs HBT, this includes precision in material growth, as well as in selective etching and patterning.
Improvements in HBT fabrication techniques that overcome any or all of the limitations of present techniques are clearly desirable.